title: Appendiceal length as an independent risk factor for acute appendicitis.
abstract: OBJECTIVE
  To determine if appendiceal lengths differ between adults with acute appendicitis and asymptomatic controls.
  
  
  METHODS
  In vivo appendiceal length at computed tomography (CT) in 321 adults with surgically proven appendicitis was compared with that in 321 consecutive asymptomatic adult controls. CT length was derived using curved multiplanar reformats along the long axis. Gross pathological length provided external validation for appendectomy cases.
  
  
  RESULTS
  Appendiceal length at CT correlated well with appendicitis specimens (mean length, 6.8 cm vs 6.6 cm; 79 % within 1.5 cm). For asymptomatic controls, mean CT appendiceal length was 7.9 cm, longer in men (8.4 ± 3.8 vs 7.4 ± 3.1 cm; P = 0.02), matching closely historical normative post-mortem data. The mean and standard deviation of appendiceal length at CT were significantly greater among negative controls than in the positive appendicitis group (7.9 ± 3.5 vs 6.8 ± 1.9 cm; P = 0.03). Of appendicitis cases, 90 % (288/321) fell within the range 4.0-10.0 cm, compared with 59 % (189/321) of negative controls (P < 0.001). Among controls, a fivefold increase in appendixes >10 cm and a twofold increase in appendixes <4 cm were observed. Half (9/18) of long appendicitis cases showed tip appendicitis at CT.
  
  
  CONCLUSIONS
  "Intermediate" appendiceal lengths (4-10 cm) are more frequently complicated by acute appendicitis, whereas both "long" (>10 cm) and "short" (<4 cm) lengths are more frequently observed in unaffected adults.
authors.affiliation: University of Wisconsin School of Medicine & Public Health, Madison, WI, USA, pj.pickhardt@hosp.wisc.edu.
authors.forename: Perry J
authors.initials: PJ
authors.lastname: Pickhardt
authors.forename: Joshua
authors.initials: J
authors.lastname: Suhonen
authors.forename: Edward M
authors.initials: EM
authors.lastname: Lawrence
authors.forename: Alejandro
authors.initials: A
authors.lastname: Muñoz del Rio
authors.forename: B Dustin
authors.initials: BD
authors.lastname: Pooler
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001062:Appendectomy / Q000592:standards; D001064:Appendicitis / Q000000981:diagnostic imaging* / Q000601:surgery; D001065:Appendix / Q000000981:diagnostic imaging*; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012307:Risk Factors; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult